How did sin^2 suddenly get into the numerator? I believe the trig-substituted integral at this point will be

[tex]\frac{1}{25} \int \frac{d\theta}{sin^2 \theta}[/tex]

Do we have an antiderivative handy for [tex]csc^2 \theta[/tex]?

BTW, please don't "bump" your own threads: it makes the reply count go up, so it looks like someone has started helping you when they actually haven't yet. Please be patient and someone will get to you. It's going to be slow right now because most universities are still on "interim" until at least next week (and many don't start up again until well into September)...

Then the replies in post #3 and the first integration in post #4 are appropriate. Find the general antiderivative of [tex]
csc^2 \theta
[/tex], then back-substitute to get the expression in terms of x.